For environmental reasons it is desirable to extend the length of time litter can be used in a pet litter box before it must be discarded. One way of accomplishing this is to have the urine pass through the litter into a tray which can be removed from the litter box and emptied rather than having the urine remain in the litter. In the past this has been accomplished by placing the litter on a screen which is located above a sloped floor which collects the urine that passes through the litter and the screen and causes it to flow through an opening into the tray. An example of such a litter box is Maguire, U.S. Pat. No. 6,408,740. However, because the litter is in direct contact with the screen and the screen has small openings, surface tension prevents some of the urine from passing through the screen. Rydman, U.S. Pat. No. 6,523,495, attempts to correct this problem by placing downwardly depending disbursing nibs at the intersection of the rows and columns of the elements in the screen. However, urine still remains in the litter.